Method and apparatus for lubricating gear pumps



Feb-l3, 1968 R, SLUUTER 3,368,799

METHOD AND APPARATUS FOR LUBRICATING GEAR PUMPS Filed March 23, 1966INVENTOR. ROBERT SLU IJTERS AGENT United States Patent Office 3,368,799Patented Feb. 13, 1968 3,368,799 METHOD AND APPARATUS FOR LUBRICATINGGEAR PUMPS Robert Sluijters, Arnhem, Netherlands, assignor to AmericanErika Corporation, Enka, N.C., a corporation of Delaware Filed Mar. 23,1966, Ser. No. 536,776 Claims priority, application Netherlands, Apr.14, 1965, 65-4,738 5 Claims. (Cl. 259-4) ABSTRACT OF THE DISCLOSUREProcess and apparatus for preventing abrasive components causing wear ingear pumps and the like metering abrasive containing materials to aliquid stream comprising continuously feeding a liquid free ofabrasivecausing components along various component pump elements, suchas a drive and rotor shaft, associated metering gears and the like;provision also is made for placing the pump in a bypass conduit whereina portion of a liquid, for example, a viscous liquid being manufacturedinto filaments, fibers and films, is used as a lubricating and flushingliquid.

This invention relates to a method and apparatus for supplying to astream of viscous liquids an additive having a relatively low viscosityand having an abrasive component of poor lubricating power.

Various methods and apparatus for supplying or injecting an additiveinto a bypass stream of a main stream of viscous liquid fiow are knownand, for example, many those skilled in the art often employ suchexpedients for adding a low viscosity titanium dioxide suspension to amain stream of a relatively high viscosity spinning solution for themanufacture of artificial threads. Usually for this purpose the additiveis preferably injected into the bypass stream between two gear typepumps. With this method and wherein gear pumps are used, the speed orrate of delivery of one gear pump is always greater than the delivery ofa second of such pumps so that between the two pumps there exists areduced pressure which is used for suction purposes and correct meteringof the masses to be admixed.

It has now been found that, particularly when an abrasive component ispresent in the liquid to be introduced, rapid wear occurs on the gearpump through which the admixed liquid last passes. An abrasive componentand/ or the relatively thin carrier liquid being introduced may easilyget between the side faces of the gears, the boundaries thereof, and theshaft bearings and as a result, the two liquids are not satisfactorilymixed. This wear is especially increased when the additive is of a lowerviscosity than the liquid being passed and considered as the mainstream.

Thus, it is the object of this invention to provide a method andapparatus for reducing or entirely avoiding wear of a gear pump used forfinally metering an injected second liquid to a main liquid flow stream.

This and other objects of the present invention are achieved bypreventing an abrasive component and/or other types of low viscosityliquids from entering and thus interfering with the bearings of saidpump by providing a continual flow of the higher viscosity liquid (forexample, the liquid being manufactured into filaments, fibers or filmand entirely free of or unmixed with the lower viscosity or abrasivecontaining liquid) along various driven parts, such as the drive shaftand associated gears of the metering pump used for introducing the lowerviscosity or abrasive contain-ing liquid to a main stream flow.

Not only does the novel method and apparatus of this invention almostentirely prevent the aforementioned wear but they also give rise tocertain advantages associated with avoiding the necessity of usingextremely accurate sealing means previously required to prevent theabrasive component and/ or low-viscosity liquid from getting tovulnerable areas within the pump. The invention also precludes thenecessity of using a special and very expensive pump lubricant whichtends to form impurities in the final product.

The highly viscous liquid stream, which serves to continually wash andlubricate the various parts of the pump, may be branched off at anypoint where the main stream has not been admixed with another liquid. Itmay be branched off from the main viscose conduit, from a supply conduitto a first gear pump, or from a discharge conduit somewhere before apoint where the additive is introduced. For practical reasons, however,it has been found particularly advantageous to branch off the higherviscosity liquid stream between a point at which the main stream isbranched off and a point where the first branch stream rejoins the mainstream.

Adequate protection from wear is obtained if, according to theinvention, a liquid stream is passed through a second branch conduit orside stream at a throughput of about 0.5 to 10% of the total ratedelivery of the pump, depending on the absolute capacity of the pump,the lubricating power of the main liquid and the additive(s), and thematerials of which the pump is made. In some cases, merely a 4%lubricating stream was found to give adequate results.

The final mixing result obtained by the present method and apparatus maybe further influenced by the rates of flow of the liquid through thevarious branches of the conduit system. A more favorable mixing resultis obtained if the proportion of the main stream passed through thefirst side stream or branch conduit is relatively large, and, accordingto the invention, it is preferred that the method be carried out whereinthe difference in the delivery rate of the first and of the second pumpin the branch line is about 5 to 20%, preferably around 10% of thedelivery rate of the second pump.

If in the pump to be protected from wear, there exists a liquid pressuregreater than the liquid pressure at the point where the second sidestream joins with the main stream, then the flow of the protectingliquid stream may be maintained without making any special provisions.It has been found that this condition is difficult to realize in actualpractice, however. It is therefore preferred that the second stream bebranched from the main stream through a gear pump in order to permit andmaintain proper flow. The gear pump can then also serve to accuratelymeter the protecting liquid stream.

It should be noted that in pumping a relatively high viscosity spinningliquid high demands are made on the uniformity of pump outputs;therefore, components of the pumps must be accurately dimensioned andplay between various parts must be very small and appreciable wear mustnot be allowed to occur.

Wear of the second gear pump in the first branch conduit is reduced evenfurther and use can be made of an even smaller protective stream,provided a low-viscosity additive (with the abrasive component) ispreviously mixed with the viscous liquid in the first branch conduitbefore flowing through the second gear pump. It is therefore preferredto have the additive mixed with the viscous liquid in the first branchconduit between the two gear pumps by means of a mechanically operatedmixer. Subsequently, and especially after the branch stream has rejoinedthe main stream, the liquid may be further passed through a mechanicalmixer or alternatively, a mixing device comprising a series ofstationary bafiles or re- 3 strictors as disclosed in commonly assignedU.S. Letters Patents Nos. 3,051,452 and 3,051,453.

To enable one to effectively carry out the method according to theinvention, the housing of the second gear pump in the first branchconduit should be provided with an additional feed inlet whichcommunicates with a system of channels that feed into openings or spacesprovided near the ends of the pump shafts and closely adjacent to theshaft sealing means therefor. In this way, the protecting liquid is ledto a point from which it may be evenly distributed along the shaftbearings and the side faces of the pump gears. Proper liquiddistribution along the side faces automatically insures properprotection of the shaft bearings. It is also preferred to use a gearpump having a gear drive shaft wherein the shaft ends are provided withhelical grooves which run to near the side faces of the gears. By use ofthis expedient, resistance to the protecting liquid flowing therethroughis reduced.

Constructing the grooves with proper directional characteristics alsoserves to effectively pump the liquid along the drive shaft.

Apparatus for effectively carrying out the invention comprises a mainspinning liquid conduit provided with a pump, e.g. a gear pump, and,beyond the pump, a bypass branch conduit in which two gear pumps arelocated and separated by an inlet for the pigment suspension. In themain conduit (and at a point where no additive has been admixed withliquid from the main conduit), there is connected a second branchconduit in which an additional gear pump is located. This second branchconduit feeds into an additionally provided feed inlet of the secondgear pump in the first branch conduit. The construction of this secondgear pump constitutes a significant portion of the invention, asdescribed above and as set out in more detail below.

Spinning liquids to which the materials may be addcd according to thisinvention comprise natural polymers such as viscose, acetate casein; orsynthetic polymers such as polyamides, aromatic polyesters,polyphenylene oxides or acrylonitriles. Suspensions to be admixed may bepigments and/ or other aids to improve the spinning process or thequality of the product, e.g., titanium dioxide.

Reference is made to the accompanying drawings and description thereofand wherein:

FIGURE 1 is a schematic representation of the apparatus according to theinvention.

FIGURE 2 shows the novel bypass and fluid flow of the gear pumpcomprising the essential elements in detail according to this invention.

In FIGURE 1, numeral 1 refers to a main conduit for a stream of viscose.The viscose is pumped through the conduits by gear pump 2. At 3, conduit4 branches off from main conduit 1 and runs through additional gearpumps 5 and 6. Between gear pumps 5 and 6, conduit 7 enters into theconduit, at which point there is located a closed mixer 8 which isprovided with convenient stirrer means. The liquid discharged by thegear pump 6 passes through the conduit 9 and re-enters the main conduit1 at connection 10.

At 11, before connection 10, a second conduit 12 branches off and runsthrough gear pump 13 to gea'r pump 6.

When the liquid streams through the conduits 1 and 9 have joined againat 10, the reunited main stream passes through mixer 14. Mixer 14 is ofthe stationary type and can be of the type disclosed in US. Patents No.3,051,452 and No. 3,051,453. Through conduit 7 a stream of a pigmentsuspension is fed to mixer 8. This stream is mixed with the stream ofviscose flowing through the branch conduit 4. Mixer 8 is conventionaland comprises a cylindrical housing having fixed pins extending radiallyinwardly from the wall. A stirrer is provided with pins which extendoutwardly and may move between the pins affixed to the walls of thecylindrical housing.

The apparatus described above serves to meter a viscous stream to afiber spinning machine.

Gear pump 2 is designed for a delivery rate of 10,000 liters/hour andpump 5 for a rate of 500 liters/hour. Pump 6 is designed for a rate of630 liters/hour. Only a fraction of these quantities, however, passesthrough the gear pump 13, namely 5 liters/hour, and serves to lubricatethe pump 6.

Through the supply conduit 7 titanium dioxide is fed to the system at arate of liters/hour.

In FIGURE 2 the gear pump 6 is shown in detail. The pump comprises part15 in which drive shaft 21 is mounted. Against part 15 there is mounteda pack of flat piates 16, 17, 18, 19, and 20. These plates are providedwith openings serving to channel the liquid (not shown) to be pumped andto receive and house the gears and the shafts.

Drive shaft 21 is rotated in the direction indicated by the arrow. Onthis shaft there is a gland 22 which is pressed against a packing system23 and insures that a liquid-tight seal is obtained between the drivingshaft and the pump.

A rotor shaft 25 connects to shaft 21 and is driven thereby via acoupling member 24. Rotor shaft 26 is driven by the intermeshing ofgears 27 and 28. All shafts inside the pump are provided with helicalgrooves 29, and with oppositely directed helical grooves 30. Suchgrooves serve to aid in the pumping of the liquid being introduced togears 27 and 28. Liquid is supplied to the bearings and grooved shaftthrough the system of channels 31 to 36. Channel 12 (shown in FIGURE 1)connects to inlet opening 31.

The gear pump 13 serves to pump a minor proportion of unmixed viscosethrough conduit 12 into the inlet opening 31. From this point thisstream of viscose flows through channels 32 to 36, passing through thegrooves 29 and 30 reaching the side faces of the gears 27 and 28. Theviscose then flows radially outwards along said faces and around thecircumferential surfaces of the gears 27 and 28 Where it is mixed withthe previously admixed viscose. Thus, viscose supplied by line 4 andcontaining an abrasive component will be prevented from penetratingbetween the side faces of gears 27 and 28, and plates 17 and 19.Accordingly, wear of said side faces and plates and of the shafts 26 and25 is prevented.

Other variations and modifications of the present invention will beapparent to those skilled in the art, and it will be understood that itis intended that the scope of the present invention be limited only bythe scope of the appended claims.

What is claimed is:

1. A method of preventing wear in metering pump moving parts used tosupply an abrasive additive to a viscous liquid solution comprisinginjecting to said pump a separate and distinct unmixed portion of saidviscous liquid to wash and lubricate said moving parts thereof and at apressure sufiicient to prevent contact of the abrasive additive withsaid parts.

2. A method as defined in claim 1 wherein said viscous liquid is aliquid used to form filaments, fibers, and film.

3. A method as defined in claim 1 and comprising providing said viscousliquid with an abrasive additive in a primary bypass stream leading froma main stream of viscous liquid flow.

4. An apparatus for admixing a pigment suspension with a spinningliquid, comprising a main spinning liquid conduit provided with a pump,a primary bypass conduit connected to the main conduit in which two gearpumps are located and separated by an inlet for the pigment suspension,and a second bypass conduit connected to said main conduit, said secondbypass conduit also provided with a gear pump for independently feedinga portion of the unmixed spinning fluid to serve as a lubricating liquidto the last gear pump located in the first bypass conduit.

5. Apparatus according to claim 4 wherein said last gear pump isprovided with a feed inlet communicating with a system of channels, saidsystem adapted for feeding an unmixed spinning liquid to a drive shaftand rotor shafts Within said pump, said shafts further having means tofeed said liquid to side faces of gear mechanisms attached to and drivenby at least one of said rotor shafts.

6 References Cited UNITED STATES PATENTS 2,986,096 5/1961 Booth et a1.30898 X WALTER A. SCHEEL, Primary Examiner.

J. M. BELL, Assistant Examiner.

